1. Field of the Invention
This invention relates to clamping pins within devices for external fixation of fractured bones, and, more particularly, to an external fixture in which pins are clamped for fixation of a fractured radius.
2. Background Information
The fracture of the distal radius is one of the most common human fractures, occurring in as many as 350,000 people per year in the United States alone. The conventional processes both for reducing such a fracture and for maintaining the bones in proper alignment during the subsequent healing process involves applying and maintaining an extension force across the fracture, with ligamental taxis being relied upon to hold the bones in place. The process for treating a fractured distal radius is described in the 1901 edition of Gray""s Anatomy in the following manner, xe2x80x9cThe treatment consists of flexing the forearm, and making a powerful extension from the wrist and elbow, depressing at the same time the radial side of the hand, and retaining the parts in that position by well-padded pistol-shaped splints.xe2x80x9d
A common method for the treatment of a fractured distal radius involves the use of standard immobilizing cast techniques, preventing movement of the radiocarpal joint throughout the course of rehabilitation. A problem with this method is that it sometimes results in inadequate internal fixation, which can cause deformity, pain, and prolonged disability.
The process of external pin fixation is often used in the repair of a fractured distal radius. This process initially involves the surgical insertion of skeletal traction pins on both sides of the fracture, with a frame being connected to the pins for immobilizing the bones, and for holding them together until the fracture is mended. Conventional methods for applying external pin fixation for the treatment of a fractured distal radius provide for the immobilization of the radiocarpal joint, so that the hand cannot be flexed.
While this type of fixation often provides an improvement over conventional casting techniques in the management of severe fractures of the distal radius, immobilization of the radiocarpal joint during the treatment period typically results in a long period of stiffness and disability after the external fixation device is removed. Typically, the external fixation device is left in place during the healing process for six to eight weeks. After the fixation device is removed, three to six months are required for the patient to regain motion of his hand.
An example of a fixation device providing adequate fixation during the healing process while allowing flexure in the radiocarpal joint is described in U.S. Pat. No. 6,197,027, the disclosure of which is incorporated herein by reference. This fixation device includes a number of pins clamped within pin mounting holes. Each pin extends through a flexible sleeve and through a clamping nut. Each pin-mounting hole includes a pilot hole guiding the pin and an internally threaded portion engaging an externally threaded portion of the clamping nut. As the clamping nut is tightened, the flexible sleeve is longitudinally compressed, so that it expands transversely to clamp itself within the pin-mounting hole and to clamp the pin within itself. The fixation device, which is configured particularly for external fixation of a fractured distal radius, includes a first number of such pins configured for attachment within a shaft portion of the radius and a second number of such pins configured to attachment to one or more fragments of the fractured radius. The fixation device also includes a sliding attachment block supporting a number of pins extending for lateral attachment to such a fragment.
However, in the holes used in the device of U.S. Pat. No. 6,197,027 to mount pins within the first number of pins, what is needed is a somewhat more simple, and therefore cost-effective, method for holding the pins in place. Such a method would preferably eliminate the need for the flexible sleeves to translate longitudinal compression into transverse clamping forces. In the holes used to mount pins within the second number of pins, what is needed is a more simple method, which will preferably clamp all of the pins in use simultaneously. Two or more of these pins may be used to clamp a single bone fragment in two or more places, or several pins may be used to clamp several bone fragments. Furthermore, since the process of setting a distal radius fracture typically includes an application of extension to the distal fragment(s), what is needed is a feature simplifying the application of such extension forces as the fixation device is installed on the fractured radius.
U.S. Pat. No. 5,545,162 describes a bone fixator including a proximal pin mounting block and a distal pin connected by a medial assembly, which connects the pin mounting blocks in a manner which is pivotally adjustable, and which further allows for adjustment of the distance between the pin mounting blocks. However, what is needed is a fixture for facilitating this distance adjustment so that it can be retained and gradually increased, instead of being lost when a clamping screw is loosened to allow movement. Furthermore, the method of U.S. Pat. No. 5,545,162 does not include the installation of pins within the fragments of bone; instead pins from the distal pin mounting block extend into the finger bones, adding a requirement that the extension forces must be directed through the wrist. To provide mobility of the hand and wrist, the fixture is pivoted with a ball joint. What is needed is a fixture rigidly holding pins extending into the bone fragments instead of into the bones of the fingers. Such a fixture would have advantages of holding different configurations of fragments in place, of holding them more rigidly, and of providing greater freedom of wrist movement.
Accordingly, it is a first objective of the present invention to provide a fixture and method for simultaneously clamping a number of pins extending into one or more fragments of a fractured bone.
It is another objective of the present invention to provide a convenient fixture and method for applying an extension to one or more fragments of bone relative to a remaining portion of bone.
According to a first aspect of the invention, a fixation device for holding a first number of pins extending into one or more fragments of a fractured bone and a second number of pins extending into another portion of the fractured bone, wherein the fixation device includes a main plate, a sliding plate, and a plate driving member. The main plate includes a first number of holes providing positions for the first plurality of pins and a second number of holes providing positions for clamping the second number of pins. The sliding plate is mounted to slide along the main plate. The sliding plate includes a third number of holes providing positions for the first number of pins as the first number of pins extend through the first plurality of holes. The plate driving member is movable in an engagement direction to slide the sliding plate along the first plate, simultaneously clamping pins extending through both the first and third pluralities of holes.
Preferably, the fixation device additionally includes a sliding pin holder slidably mounted on the main plate and releasably clamped in place on the main plate. A hole within the second number of holes extends within the sliding pin holder. Sliding the sliding pin holder in an extension-increasing direction increases a distance between a pin extending through the sliding pin holder and a pin extending through each hole in the first plurality of holes. Preferably, this fixation device also includes a frame removably attached to a pin extending through the sliding pin holder, and a setscrew moving the frame in the extension increasing direction.
According to another aspect of the invention, a method is provided for fixing one or more fragments of a fractured bone in place with respect to another portion of the fractured bone. The method includes:
a) surgically inserting a first plurality of pins, to extend through holes in a first plurality of holes within a main plate of a fixation device, into the one or more fragments of fractured bone;
b) clamping the first plurality of pins within holes in the first plurality of holes;
c) surgically inserting a sliding pin to extend through a hole within a sliding pin holder, mounted to slid along the main plate of the fixation device, into an other portion of the fractured bone;
d) after completing steps a) through c), sliding the sliding pin holder to establish extension between the one or more fragments of fractured bone and the other portion of fractured bone; and
e) clamping the sliding pin holder in a location established in step c) to maintain the extension.